Kleiner Perkins' partner Mary Meeker suggested that the private markets are a bit bubbly right now.

On stage at the All Things D conference, she said Kleiner has a $1 billion digital growth fund, and it didn't invest a penny in the March quarter. The reason? "We couldn't couldn't get comfortable with valuations."

And she thinks this could eventually lead to the private market bubble bursting.

She says that the valuations in the private market are going to make it "difficult to go public." The valuations make it "difficult to justify the goals." The prices are going up and up. And the businesses are not keeping up.

So, when these companies start to look for public market exits, there's a good chance the "private market will lose money."